Typical aircraft communicate with systems on the ground during the course of a flight using a very high frequency (VHF) communications apparatus that operates in a frequency band allocated to aircraft operation. For example, voice communications between aircraft and ground-based air traffic control facilities are generally carried out by means of a VHF communications transceiver that operates in a frequency band from 118.0 MHz to 135.95 MHz on any of a plurality of selectable and discrete channel frequencies in this band. Data may also be communicated between a ground station and an aircraft by coupling a modem to the VHF communications transceiver so that data may be communicated using audio frequency tones. For example, the well-known Aircraft Communications Addressing and Reporting System (ACARS) and the Aeronautical Telecommunications Network (ATN) provide a data link capability so that character-oriented and bit-oriented communications may occur between the ground station and the aircraft.
Since VHF networks are generally limited to line-of-sight propagation, multiple ground stations are needed to communicate with the aircraft during a flight of any significant distance. In particular, as the aircraft traverses its flight path, it will switch to a new ground station based on various factors such as the signal strength of the current ground station and the signal strength of the other ground stations within range of the aircraft. Although, switching to a new ground station is typically done to improve signal strength, each switch between ground stations involves executing hand-off procedures which can also increase network congestion. Since limited channels are allocated for aircraft communications, it is desirable to limit the number of ground station hand-offs in order to limit the increase in network congestion.